Yes, I use such a filter on all of my guide cameras as it does improve focus and therefore star/centriod quality, especially when using simple achromat refractors (which is what most of us use). One thing I would recommend, though, is to get a larger guide scope. Given that you want to have really fast guide exposures/pulses (one second maximum, preferably 0.5 seconds), more aperture gets you more light and better and more numerous stars to guide from. 50 and 60 mm achromat guide scopes are pretty inexpensive and have decent enough quality to serve the purpose.
